Telephone-exchange system.



PATBNTED AUG. 1, 1905.

E. R. GORWIN. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED 81113123, 1904.

m l l l l Wei/2055649; .M i.

UNITED STATES PATENT OFFICE.

TELEPHONE-EXCHANGE -SYSTEM.

No.f795.961.

Specification of Letters Patent.

Patented Aug. 1, 1905.

Application filed September 3, 190a. Serial No. 223,169.

To all whom it YIIIIII/ concern.-

Be it known that I, ELMER R. CoRwrN, a citizen of the United States of America, and a resident of Chicago, county of Cook, and State of Illinois, have invented a new and useful Improvement in Telephone-Exchange Systems, of which the following is an exact and concise description, reference being had to the accompanying drawing, which forms a part of this specification.

My invention relates to the class of telephone systems in which there is a central source of electrical energy for the signals. In such systems now of general commercial use itis usual to arrange the circuits of the connecting-cords in such a manner that the operator may connect her telephone with the talking-conductors of the cord-circuit not only at the time of answering a call, but at any time during the progress or after the close of a conversation. Before the introduction of the present generally-used system of automatic supervisory signals, indicating at all times the condition of the circuits with reference to conversation, it was necessary to provide the operator with this means of connectingewith the talking-conductors of the cord-circuit in order that she might ascertain that the conversation was begun or whether it had been completed. This was the more necessary, because clearing-out signals given by the subscribers at the close of conversation were unreliable, due to neglect on the part of subscribers or to other causes. The advent of the before-mentioned automatic supervisory signals removes the necessity of this frequent listening in on a connection.

One of the objects of my invention is to provide means for all necessary listening in and means for preventing all unnecessary listening in on the part of the operator.

In by far the greater portion of the centralenergy lamp-signal telephone equipments in use at the present time the signalassociated with the subscribers line for indicating that he is making a call is an incandescent lamp lighted by the closing of a relay-contact when the subscriber removes the receiver from its hook. In many of these systems, also, there called subscriber answers.

eliminates these relays and accomplishes the necessary results of operation in a manner similar to the standard way, but at a smaller cost for the equipment of the teleph ne cen tral ofiice.

I attain these objects by means of the circuits and mechanism shown in the accompanying drawing, which is a view of two line-circuits, a cord-circuit, and an operators telephone-circuit.

Referring to the drawing, 1 is a battery or other generator of electricity located in the central oflice. I

2 is a subscribers' telephone set of the usual type adapted to allow direct currents to be passed when the receiver is off the hook and not when it is on.

3 and 4 are the line conductors of the metallic circuit connecting the subscribers instrument with the central ofiice.

5 and 6 are two of the multiple jacks which appear in the face of the multiple switchboard in the central oflice as points of access with the subscribers line in question. 7 is the signal-lamp associated with that line. Of the spring-jacks 5 and 6 and others of the group connected with a given line one may be associated with other apparatus in such a position as to be used for the answering of all calls, the remainder being used only for the connection of other lines which make calls for it. The parts and electrical conditions of the answering-jack and the multiple jacks are quite the same. The parts of a given jack are shown with reference to the jack 5, in which 8 is a test-bushing connected with all similar parts of other jacks of a given line and normally with nothing else.

9, 10, and 11 are springs adapted to register with parts of a plug to be described later, and 12 is a contact-piece adapted to make contact with the spring 9 when the jack is not occupied by a plug. The springs 10 and 11 are adapted to come into electrical contact with each other unless the plug is in the jack, and such contact will be broken when the connection is made with the jack by means of the plug. Similar relations of parts exist in all jacks as in the jack 6 and as in the jacks 5" and 6 of the line connecting with the subscribers set 2, shown at the right of the drawing.

Should the subscriber having the station set 2 remove his receiver from the hook, the circuit conditions will be as follows: Current will I flow from the ungrounded side of the battery 1 in the central oifice through the signal-lamp 7 from the contact-spring 13, to the spring 14 and the contact-piece 12, to the spring 9, over the wire 4, to and through the subscribers telephone 2, over the wire 3, to jack 5 in the central office and to spring thereof, through the contact to the spring 11, thence to jack 6 and the spring 15, through the contact to the spring 16, and thence to the grounded side of the central-oflice battery.

The signal-lamp 7 is of such electrical dimensions at to be capable of giving a practical signal with the current which will flow through it over a line of reasonable maximum length and resistance and also of withstanding the full voltage of the batter or generator in case a short circuit should occur, lighting the lamp over a circuit of negligible resistance.

The arrangement of the circuits and the operation of the line-signal are quite the same with reference to all other lines of the system as represented with reference to the substation set 2, shown at the right of the sheet.

The cord-circuits of my system by means of which the operator makes connections between the calling-lines and called lines are uniform in type and are represented by that part of the drawing shown between the plugs designated as units 17 and 18. Of the plugs,17 19 is a tip, 20 is a middle contact or ring, and 21 .is a shank 'or sleeve. A conductor leads through the flexible cord to each of these points. The tip 19 is adapted to engage a spring, as 11, of a jack, the ring 20 is adapted to engage a spring, as 10, of ajack, and the sleeve 21 is adapted not only to make contact with the test ring or bushing, as 8, but to make contact as well and at the same time with another spring, as 9, of a jack. When the plug makes these engagements, contacts are broken within the jack, as already described. The plug which I have designated 17 is that which in my system is used for answering calls, and the plug 18 is used for connecting with lines called. Of the plug 17 the conductors from the tip, ring, and sleeve, respectively, lead to the springs 22, 23, and 24 of the listening-key 25. In the drawing 1 show this listening-key in proper position for conversation to proceed. The supervisory signal-lamp 26 has one of its terminals con nected with the spring 27 of this listeningkey. Thislamp 26is that which is associated with the answering-plug 17. The supervisory lamp 28 has one of its terminals connected to the spring 29 of the listening-key. This supervisory lamp is that which is associated with the calling-plug 18. The other terminal of the lamp 26 is connected to the back con tact 30 of the relay 31, the armature 32 of which is connected with the ungrounded side of the battery. The corresponding terminal of the supervisory lamp 28 is connected to the back contact 33 of the relay 34, the armature 35 of which is also connected with the ungrounded side of the battery. The relays 31 and 34Iprefer to make of high resistance. The functions of their remaining parts and the connections of their windings I describe later. Two impedance-coils 36 and 37 of im pedance substantially equivalent to the impedance of the relays 31 and 34 are connected to the cord-circuit, one terminal of each being grounded.

The operators telephone-circuit consists of the usual portable receiver, induction-coil, transmitter, and source of current. I provide an additional element in the repeatingcoil 38, of which 39 is the secondary winding. 40 and 41 are two primary windings. The point of junction between the windings 40 and 41 is connected to ground. The free terminals of these primary windings are connected, respectively, to the springs 43 and 42 of the listening-key.

Considering the secondary 44 of the induction-coil 45, the receiver 46, the secondary 39 of the repeating-coil 38, and the condenser 47 as a single unit forming the operators telephone set, one terminal leading to the con denser 47 is connected to the spring 48 of the listening-key. The other, leading from the secondary 44,connects with two contact-pieces 51 and 52, here first mentioned, associated, respectively, with the relays 31 and 34. When these relays are not energized,the armature 49 makes connection with its back contact 51,and the armature 50 makes connection with its back contact 52. The result of the makingof either or both of these contacts is to extend the telephone-circuit to the spring 53 of the listeningkey. If the listening-key be actuated during this condition of the relays 31'and 34, the telephone-circuit will be connected directly to the ring and sleeve portions of the plug 17 and through the condensers 54 and 55 'with the corresponding parts of the plug 18. This latter path is by way of the ringing-key 56, which is of a usual type and adapted to send ringing-current from the generator 57 over the conductors of a called line, at the same time breaking contact with the conductors leading to the answering-plug. With reference to the condensers 54 and 55, inserted serially in the conductors between the ring and sleeve portions of the plugs 17 and 18, the relay 31 has one end of its winding connected to one side of the condenser 55 and the relay 34 one side of its winding to the other side. The remaining terminals of the windings of the relays 31 and 34 are connected to the ungrounded terminal of the battery 1. Similarly the ungrounded terminal of the impedance-coil 36 connects to one terminal of the condenser 54' and one terminal of the impedance-coil 37 to the remaining terminal of the condenser 54. The result of these conditions is to permit current from the battery 1 to be supplied to the calling-line through the impedance=coil 36 and the relay 31 and to the called line through the impedance-coil 37 and the relay 34. During a connection if the receiver at either of the two substations involved is on its hook the corresponding contact-o1 armature 49 against point 51 or armature 50 against point 52 will be closed, and it will be possible. for the operator to listen in on the line by actuating the key 25. During the time, however, that both receivers are oil" the hooks and the condition of actual conversation exists such listening in will be impossible, because the contacts at 51 and 52 will both be open.

As all test-bushings of the jacks of a given line are connected to each other and normally to nothing else and as the electrical condition of the sleeves of plugs is always that of a ditlerence of potential with reference to ground, the existence of a plug in a jack will give these test-bushings a difference of potential also with reference to ground. When the operator actuates her listening-key, secures an order from a calling subscriber, and desires to test the line which is called, she is enabled to do so because the conductor from the tip 58 of the calling-plug 18 is led via the spring 61 of the listeningkey 25 and the contact of the spring 42 to the ungrounded terminal of the primary winding 41 ot' the repeating-coil 38 and through that winding to ground. As the operators receiver-circuit is associated with the secondary of this repeating-coil and as the listening-circuit of her set is closed, contacts of the tip 58 of the plug 18 with the test-bushings of any busy line will cause a click of the well-known significance. In the absence of any connection on the line no such click will be heard, as the test-ring of that line will haye no potential with reference to the earth. Similarly a contact between springs 22 and 43 of the listening-key enables a test to be made by the tip 19 of the answering-plug 17, so that so far as testing is concerned the answering and calling plugs are capable of being used interchangeably.

It will be seen that one of the distinct actions of the listening-key 25 is to convert the tip-circuits of the two plugs of the cord-circuit from being parts of the testing-circuits to being parts of the supervisory circuits, or Vice versa.

I have described the relation of the supervisory lamps 26 and 28 to the relays 31 and 34, which respectively control them. When the connection has been set up, the act of the operator with reference to the listening-key 25 is to disconnect her telephone from the cord-circuit, which she does by releasing the key. This reconnects the spring 27 with the spring 22, extending the free terminal of the lamp 26 to the tip 19 of the plug 17. It also similarly extends the free terminal of the lamp 28 through contacts between the springs 29 and 61 to the tip 58 of the plug 18; but the tip 19, inserted in any jack of a line, will find a ground connection either immediately, as by contact with spring 16 of the jack 6, or through the described series of contacts, as from the spring 11 of the jack 5. A similar condition will result with respect to a calling-plug, as 18, in connection with any jack and line with which it may be connected. If the subscriber has his telephone from the hook and, as in the case of the assumed calling subscriber at station 2, is drawing current through the relay 31, the lamp 26 will not be lighted, because its circuit is open at the contact of armature 32 and point 30. In the case of a called subscriber, as station 2, the lamp 28 will be lighted, because the relay 34 is not energized. The lamp will then give the usual signal that ringing must be continued and will be extinguished only when a response is secured from the subscriber. It will further be relighted upon the hanging up of the receiver of the called subscriber, as will lamp 26 when the calling subscriber hangs up his receiver. Upon the operator obeying the signal for disconnection, indicated by the lighting ofboth lamps, the taking out of the plugs from the spring-jacks will again extinguish the lamps. Upon the lighting of one or the other lamp alone, indicating, perhaps, a disconnection being desired or perhaps a doubt as to what is wanted, the

operator may actuate her listening-key, connecting her telephone with the circuit, but extinguishing the signal-lamps by the breaking of the described contacts, these lamps not being required for purposes of her information during the time when her telephone is connected with the cord-circuit.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is

1. In a telephone-exchange system, substation-telephones, an operators telephone-circuit, a cord-circuit, telephone-line circuits, and two supervisory relays in said cord-circuit, each provided with an armature and back contact in shunt with each other and in series with said operators telephone-circuit, and constituting means by which said operators telephone-circuit is prevented from listening connection with said cord-circuit when both the receivers of the telephones of two of said substation-telephones connected by said cord-circuit, are ofl their hooks, substantially as described.

2. In combination in a telephone system, an operators telephone-circuit, a cord-circuit, telephone-lines, telephone-substation sets, a relay associated with each plug of said cordcircuit, a contact normally closed under control of each said relays, said contacts being normally in shunt with each other and in series with said -operators telephone-circuit, permitting speaking connection between said cord-circuit, and said operators telephonecircuit when two of said operators telephonelines are connected through said cord-circuit, and the receiver at but one of said telephonesubstation sets is ofi the hook, substantially as described.

3. In a telephone system, substation-telephones, telephone-lines, a cord-circuit, cordcircuit relays associated therewith, an operators telephone set, an operators listeningkey, and two switches directly controlled by said relays and in shunt with each other, and in series with said operators telephone set, each said switches being held open by its said controlling-relay when energized, substantially as described.

4. In a telephone system, a listening-key, an operators test-circuit, connecting-plugs, supervisory signals, and means whereby the actuation of the listening-key will place the said test-circuit in testing connection with said connecting-plugs, and means whereby the release of said listening-key will place the said supervisory signals in connection with said connecting-plugs, substantially as described.

5. In a telephone system, supervisory signals, an operators telephone-circuit, a listening-key connected thereto, and two supervisory relays, each controlling two switches, normally closed, one adapted when its relay is energized to extinguish its said associated supervisory signal and the other to open a shunt path about the homologous switch of the other relay, and both homologous switches by simultaneous action to open said operators telephonecircuit, substantially as described.

6. In combination in a telephone-exchange system, substation-telephones, an operators telephone-circuit, a cord-circuit adapted to form a link for interconnecting two of said lines,supervisory signals, cord-circuit relays,a listening-key adapted when operated to bridge said operators telephone-circuit across the two said telephone-lines in said cord-circuit, normally closed contacts directly controlled by said relays, said contacts being in shunt with each other and in series with said operators telephone-circuit, and adapted to open said operators telephone-circuit when conditions for conversation are established at the said substation-telephones on the two said telephone-lines so connected, substantially as described.

7. In a circuit-changing device, a springjack, 5, having the test-bushing, 8, the springs, 9, 10 and 11, the contact-piece, 12, and adapted to maintain normal contact between parts, 10 and 11, and 9 and 12; a plug, 17, having the tip, 19, the ring, 20, and the sleeve or shank, QLadapted to register part, 21, with parts, 8 and 9, and part, 20, with part, 10, and part, 19, with part, 11, breaking the said normal contacts, substantially asdescribed.

8. In a telephone test-circuit for multiple switchboards, two plugs, a cord-circuit associated therewith, an operators telephone-circuit, a repeating-coll havlng three windings in mutual inductive relation, one of said windings being electrically connected to each of said plugs and the third to the said operators circuit, and means whereby a test-contact between one of said plugs and a test-bushing of a busy line will be audible in said operators telephone-circuit, substantially as described.

9. In a cord-circuit for telephone-switchboards, two plugs, two condensers, two conductors joining said plugs serially through said condensers, a listening-key, two supervisory relays, an operators telephone-circuit adapted to be connected as a bridge upon said conductors and in series with said listeningkey and contacts of said supervisory relays, and means whereby either the operation of said listening-key or said relays will interrupt said operators telephone-circuit,substantially as described.

10. In combination, a telephone cord-circuit, an operators telephone-circuit, an operators test-circuit, a listening-key, supervisory signal-circuits, and means whereby the movements of said listening-key may interchange the association of said supervisory signal-circuits and said operators test-circuit with said cord-circuit, substantially as described.

11. In a telephone system, a cord-circuit, an operators telephone-circuit, a listeningkey, a test-circuit, two supervisory relays, each having two armatures and two contacts, two supervisory signals each under control of an armature of one said relay, and alink comprising one armature and contact of each said relay, in series with said operators telephonecircuit, adapted to open said operators telephone-circuit when both said supervisory relays are energized, substantially as described.

12. In a telephone system, a cord-circuit, an operators telephone-circuit, a listeningkey, a test-circuit, two supervisory relays, each having two armatures and two contacts, two supervisory signals, each under control of an armature of one said relay, a link comprising one armature and contact of each said relay, in series with said operators telephonecireuit, adapted to open said operators telephone-circuit when both said supervisory relays are energized, and means adapting said listening-key to interchange the association of said supervisory signal-circuits and said test-circuit with said cord-circuit, substantially as described.

Signed by me at Chicago, county of Cook, State of Illinois, in the presence of two witnesses.

ELMER R. CORWIN.

Witnesses:

SAMUEL Gr. MGMEEN, H. G. PRADO. 

